Image Display Apparatus and Optical Component

ABSTRACT

This image display apparatus includes laser beam source portions, a synthesized beam generation portion, a control portion, a branching unit, and a detection portion, while the branching unit has a reflectance or transmittance with increase/decrease characteristics opposite to increase/decrease characteristics of the outputs of laser beams in increasing or decreasing the outputs of the laser beams of color components according to changes of the wavelengths of the laser beams of the color components in order to maintain the prescribed color state of a synthesized beam.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of Japanese ApplicationSerial No. 2012-205896, with a filing date of Sep. 19, 2012, and claimsthe benefit of Japanese Application Series No. 2013-166850, with afiling date of Aug. 9, 2013.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image display apparatus synthesizinga plurality of laser beams of different color components to project acolor image and an optical component utilized in such an image displayapparatus, exhibiting a prescribed reflectance or transmittance for alaser beam of a prescribed wavelength.

2. Description of the Background Art

Various image display apparatuses, such as a laser projector, eachsynthesizing laser beams of a red color component (R), a green colorcomponent (G), and a blue color component (B) to project and display acolor image on a projection surface are put to practical use. Such animage display apparatus must maintain the color state of a beam obtainedby synthesizing laser beams of R, G, and B in a prescribed state inorder to project and display a color image with high colorreproducibility. Typically, the white balance of the beam obtained bysynthesizing the laser beams of R, G, and B must be created.

Japanese Patent Laying-Open No. 2004-226631 discloses a projectorincluding a first light source portion, a second light source portion, athird light source portion, a temperature detection portion detectingthe temperature of each light source portion, a spatial light modulatormodulating light from each light source portion according to an imagesignal, a projection lens projecting the light modulated by the spatiallight modulator on a screen, a storage portion storing a relationshipbetween the temperature of each light source portion and a luminancedistribution of each color light from each light source portion, and acontrol portion controlling the spatial light modulator to substantiallyuniform the luminance distributions of the color light on the screen onthe basis of the relationship between the temperature of each lightsource portion detected by each temperature detection portion and theluminance distribution of each color light stored in the storage portionin order to reduce irregular colors correspondingly to a change ofirregular color distribution following a change of the temperature ofeach light source portion.

Japanese Patent Laying-Open No. 2008-003270 discloses the structure of aprojection image display apparatus partially emitting a beam combinedinto a white beam to a light detection portion, allowing the beam to beincident on a photo sensor having a color filter mounted on aphotodiode, comparing a signal indicating the light quantity of the beamoutput from the photo sensor with a signal value in previous adjustmentof a white balance by changes of the light quantities of R, G, and B ina control portion, and changing the drive gain of each light source inorder to reduce a difference between the light quantities to adjust thechromaticity of white.

Japanese Patent No. 2663437 discloses a semiconductor laser apparatusconfigured to reduce a fluctuation in the intensity of output lightresulting from a temperature change by rendering thetemperature-dependent characteristics of the intensity of monitor lightemitted from a semiconductor laser element and the temperature-dependentcharacteristics of the detection output of a light receiving elementopposite to each other. In this semiconductor laser apparatus, nocontrol for achieving a prescribed color state such as a white balancecorrespondingly to a wavelength change is performed.

As described above, in the image display apparatus projecting the colorimage, it is necessary to create the white balance, but a change of theoutput light quantity of each light source and a change of the outputwavelength of each light source cause loss of this white balance. Inother words, a state where the white balance is created denotes a statewhere the light quantity (namely, the output of each light source)thereof is a prescribed value with respect to the wavelength of the beamof each color component forming a synthesized beam, and when thewavelength of the output of each light source changes, the white balanceis lost unless each light source outputs a prescribed light quantitywith the changed wavelength.

In the image display apparatus, an element such as an LD (a laser diode)is employed as a laser beam source for each color component, but thewavelength of an output laser beam changes due to a temperature change.On the other hand, the image display apparatus is employed in variousenvironments and is provided with a component generating heat byoperation in addition to the laser beam source, so that the temperatureof the laser beam source changes and the wavelength of the laser beamoutput therefrom changes. In the case where the white balance isadjusted on the basis of the light quantity (the luminance) of the laserbeam, the white balance of a synthesized laser beam is disadvantageouslylost when the wavelength of the laser beam changes.

SUMMARY OF THE INVENTION

The present invention has been proposed in order to solve theaforementioned problem, and an object of the present invention is tomaintain a prescribed color state such as a white balance even when thewavelength of a laser beam changes.

An image display apparatus according to a first aspect of the presentinvention includes a plurality of laser beam source portions outputtinglaser beams of a plurality of color components different from eachother, a synthesized beam generation portion synthesizing the laserbeams of the plurality of color components to generate a synthesizedbeam, a control portion controlling the outputs of the laser beam sourceportions, a branching unit branching the laser beams of the colorcomponents, and a detection portion detecting the light quantities ofthe laser beams of the color components branched by the branching unit,while the branching unit has a reflectance or transmittance withincrease/decrease characteristics opposite to the increase/decreasecharacteristics of the outputs of the laser beams in increasing ordecreasing the outputs of the laser beams of the color componentsaccording to changes of the wavelengths of the laser beams of the colorcomponents in order to maintain the prescribed color state of thesynthesized beam, and the control portion is configured to control theoutputs of the laser beam source portions according to the lightquantities of branched laser beams of the color components detected bythe detection portion.

As hereinabove described, the image display apparatus according to thefirst aspect is provided with the branching unit having the reflectanceor transmittance with the increase/decrease characteristics opposite tothe increase/decrease characteristics of the outputs of the laser beamsin increasing or decreasing the outputs of the laser beams of the colorcomponents according to the changes of the wavelengths of the laserbeams of the color components in order to maintain the prescribed colorstate of the synthesized beam, whereby even when the wavelengths of thelaser beams change, the outputs of the laser beam source portions arecontrolled according to the light quantities of the laser beams of thecolor components branched by the branching unit and detected by thedetection portion, so that the prescribed color state such as a whitebalance can be maintained.

In the aforementioned image display apparatus according to the firstaspect, the control portion is preferably configured to decrease theoutputs of the laser beam source portions for the color components whosedetected light quantities are increased and increase the outputs of thelaser beam source portions for the color components whose detected lightquantities are decreased according to the light quantities of thebranched laser beams of the color components detected by the detectionportion. According to this structure, the outputs of the laser beamsource portions are adjusted in such directions as to cancel the changesof the detected light quantities, whereby the prescribed color state canbe easily maintained.

In the aforementioned image display apparatus according to the firstaspect, the control portion is preferably configured to increase theoutputs of a blue laser beam source outputting a laser beam of a bluecolor component and a red laser beam source outputting a laser beam of ared color component and decrease the output of a green laser beam sourceoutputting a laser beam of a green color component when the wavelengthsof the laser beams of the color components output from the laser beamsource portions are increased due to a temperature rise. According tothis structure, even when the wavelengths of the laser beams of thecolor components output from the laser beam source portions areincreased due to a temperature rise, the prescribed color state can beeasily maintained by increasing the outputs of the laser beam source ofthe blue color component and the laser beam source of the red colorcomponent and decreasing the output of the laser beam source of thegreen color component.

In the aforementioned image display apparatus according to the firstaspect, the branching unit is preferably so configured that thereflectance or transmittance thereof changes according to the changes ofthe wavelengths of the laser beams. According to this structure, thechanges of the wavelengths of the laser beams can be easily detected bythe changes of the light quantities of the laser beams of the colorcomponents branched by the branching unit.

In this case, the branching unit is preferably so configured that thereflectance or transmittance thereof decreases when the wavelengths ofthe laser beam of the blue color component and the laser beam of the redcolor component are increased and increases when the wavelength of thelaser beam of the green color component is increased. According to thisstructure, the changes of the wavelengths of the laser beams of theblue, red, and green color components are easily detected and theoutputs of the laser beam source portions for the blue, red, and greencolor components are adjusted by the control portion, whereby theprescribed color state can be easily maintained.

In the aforementioned image display apparatus according to the firstaspect, the branching unit is preferably so configured that thereflectance or transmittance thereof for the laser beam of the bluecolor component is highest, the reflectance or transmittance thereof forthe laser beam of the red color component is lowest, and the reflectanceor transmittance thereof for the laser beam of the green color componentis between the reflectance or transmittance thereof for the laser beamof the blue color component and the reflectance or transmittance thereoffor the laser beam of the red color component. According to thisstructure, the light quantity of the laser beam of the blue colorcomponent whose wavelength is short and for which the detectionsensitivity is low, being incident on the detection portion isincreased, and the light quantity of the laser beam of the red colorcomponent whose wavelength is long and for which the detectionsensitivity is high, being incident on the detection portion isdecreased. Therefore, the detection portion can reliably detect thelaser beams of the red color component, the green color component, andthe blue color component without increasing the range of the detectionsensitivity of the detection portion for the laser beams.

In the aforementioned image display apparatus according to the firstaspect, the prescribed color state preferably includes a state where thewhite balance of the synthesized beam is created. According to thisstructure, even when the wavelengths of the laser beams change, thestate where the white balance is created can be maintained.

In the aforementioned image display apparatus according to the firstaspect, the branching unit preferably includes a prism formed with adielectric multi-layer having a reflectance or transmittance withincrease/decrease characteristics opposite to the increase/decreasecharacteristics of the outputs of the laser beams. According to thisstructure, due to the dielectric multi-layer, the branching unit havingthe reflectance or transmittance with the increase/decreasecharacteristics opposite to the increase/decrease characteristics of theoutputs of the laser beams in increasing or decreasing the outputs ofthe laser beams of the color components according to the changes of thewavelengths of the laser beams of the color components in order tomaintain the prescribed color state of the synthesized beam can beeasily provided. Furthermore, the branching unit includes the prismformed with the dielectric multi-layer, whereby the branching unit canbe employed with the function of the prism in addition to a function ofbranching the beam.

In the aforementioned image display apparatus according to the firstaspect, the branching unit is preferably provided in the optical path ofthe synthesized beam, and the control portion is preferably configuredto allow a laser beam source portion for any one of the color componentsto output a laser beam during image display with the synthesized beamand control the output of the laser beam source portion according to thelight quantity of a branched laser beam of a single color componentdetected by the detection portion. According to this structure, thebranching unit and the detection portion can be shared for the colorcomponents, and hence the number of components can be reduced.

In the aforementioned structure having the branching unit provided inthe optical path of the synthesized beam, the control portion ispreferably configured to allow the plurality of laser beam sourceportions one by one to sequentially output the laser beams during theimage display with the synthesized beam and control the outputs of thelaser beam source portions according to the light quantities of thebranched laser beams of the color components detected by the detectionportion. According to this structure, the laser beams of the colorcomponents can be detected individually, and hence the changes of thelight quantities of the laser beams of the color components can be moreaccurately detected.

In the aforementioned structure having the branching unit provided inthe optical path of the synthesized beam, the control portion ispreferably configured to allow the laser beam source portion for any oneof the color components to output the laser beam for detecting the lightquantity at an interval of a prescribed number of frames during theimage display with the synthesized beam and control the output of thelaser beam source portion according to the light quantity of thebranched laser beam of the single color component detected by thedetection portion. According to this structure, even when the wavelengthof the laser beam changes during the image display, the output of thelaser beam source portion can be adjusted according to the change of thelight quantity detected by the detection portion, and hence theprescribed color state such as the white balance during the imagedisplay can be easily maintained.

In the aforementioned structure having the branching unit provided inthe optical path of the synthesized beam, the control portion ispreferably configured to switch between a first mode in which an imageis continuously displayed without detection of the light quantity and asecond mode in which the laser beam is output from the laser beam sourceportion for any one of the color components during the image displaywith the synthesized beam and the light quantity of the laser beam isdetected. According to this structure, the prescribed color state suchas the white balance during the image display can be easily maintainedby the second mode while the image is continuously smoothly displayedwithout detection of the light quantity by the first mode.

The aforementioned image display apparatus according to the first aspectpreferably further includes a scan portion scanning the synthesizedbeam, and the branching unit is preferably arranged between thesynthesized beam generation portion and the scan portion in the opticalpath of the synthesized beam. According to this structure, the branchingunit can be arranged at a position on which the laser beams of the colorcomponents are focused, and hence increase in the size of the branchingunit can be inhibited.

In this case, the scan portion preferably includes a MEMS (micro electromechanical system) scan mirror. According to this structure, with theMEMS scan mirror, downsizing in the scan portion, low power consumption,speeding up of processing, etc. can be achieved.

In the aforementioned image display apparatus according to the firstaspect, the synthesized beam generation portion preferably includes adichroic mirror. According to this structure, with the dichroic mirror,the accuracy of color synthesis can be improved, and the durability ofthe synthesized beam generation portion can be improved.

An optical component according to a second aspect of the presentinvention has a reflectance or transmittance with increase/decreasecharacteristics opposite to increase/decrease characteristics of theoutputs of laser beams in increasing or decreasing the outputs of thelaser beams of a plurality of color components according to changes ofthe wavelengths of the laser beams of the color components in order tomaintain a synthesized beam obtained by synthesizing the laser beams ofthe color components in a prescribed color state, is provided in animage display apparatus comprising a detection portion detecting thelight quantities of the laser beams and a control portion controllingthe outputs of a plurality of laser beam source portions outputting thelaser beams of the plurality of color components different from eachother according to the detection results of the detection portion, andincludes a branching unit branching the laser beams of the colorcomponents and guiding the laser beams to the detection portion.

In the optical component according to the second aspect, as hereinabovedescribed, the branching unit is configured to have the reflectance ortransmittance with the increase/decrease characteristics opposite to theincrease/decrease characteristics of the outputs of the laser beams inincreasing or decreasing the outputs of the laser beams of the colorcomponents according to the changes of the wavelengths of the laserbeams of the color components in order to maintain the prescribed colorstate of the synthesized beam, whereby even when the wavelengths of thelaser beams change, the outputs of the laser beam source portions arecontrolled according to the light quantities of the laser beams of thecolor components branched by the branching unit and detected by thedetection portion, so that the prescribed color state such as a whitebalance can be maintained.

In the aforementioned optical component according to the second aspect,the control portion is preferably configured to decrease the outputs ofthe laser beam source portions for the color components whose detectedlight quantities are increased and increase the outputs of the laserbeam source portions for the color components whose detected lightquantities are decreased according to the light quantities of branchedlaser beams of the color components detected by the detection portion.According to this structure, the outputs of the laser beam sourceportions are adjusted in such directions as to cancel the changes of thedetected light quantities, whereby the prescribed color state can beeasily maintained.

In the aforementioned optical component according to the second aspect,the branching unit is preferably so configured that the reflectance ortransmittance thereof changes according to the changes of thewavelengths of the laser beams. According to this structure, the changesof the wavelengths of the laser beams can be easily detected by thechanges of the light quantities of the laser beams of the colorcomponents branched by the branching unit.

In this case, the branching unit is preferably so configured that thereflectance or transmittance thereof decreases when the wavelengths of alaser beam of a blue color component and a laser beam of a red colorcomponent are increased and increases when the wavelength of a laserbeam of a green color component is increased. According to thisstructure, the changes of the wavelengths of the laser beams of theblue, red, and green color components are easily detected and theoutputs of the laser beam source portions for the blue, red, and greencolor components are adjusted by the control portion, whereby theprescribed color state can be easily maintained.

In the aforementioned optical component according to the second aspect,the branching unit is preferably so configured that the reflectance ortransmittance thereof for the laser beam of the blue color component ishighest, the reflectance or transmittance thereof for the laser beam ofthe red color component is lowest, and the reflectance or transmittancethereof for the laser beam of the green color component is between thereflectance or transmittance thereof for the laser beam of the bluecolor component and the reflectance or transmittance thereof for thelaser beam of the red color component. According to this structure, thelight quantity of the laser beam of the blue color component whosewavelength is short and for which the detection sensitivity is low,being incident on the detection portion is increased, and the lightquantity of the laser beam of the red color component whose wavelengthis long and for which the detection sensitivity is high, being incidenton the detection portion is decreased. Therefore, the detection portioncan reliably detect the laser beams of the red color component, thegreen color component, and the blue color component without increasingthe range of the detection sensitivity of the detection portion for thelaser beams.

The control portion according to the present invention can have acircuit configuration employing an electronic component and also can beconfigured as a functional module employing computer hardware andsoftware and so configured that the computer hardware executes thesoftware.

According to the present invention, in the image display apparatus, theprescribed color state such as the white balance can be maintained evenwhen the wavelengths of the laser beams change.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the structure of a main section of an image displayapparatus according to an embodiment of the present invention;

FIG. 2 illustrates a branching unit according to the embodiment of thepresent invention;

FIG. 3 illustrates a relationship between a wavelength and thereflectance of a reflective film;

FIG. 4 illustrates relationships between the wavelengths and outputs oflaser beam sources for maintaining a white balance according to theembodiment of the present invention; view (a) illustratescharacteristics at a temperature of 25° C.; view (b) illustratescharacteristics at a temperature of 50° C.; view (c) illustratescharacteristics at a temperature of 50° C.

FIG. 5 illustrates the reflectance characteristics of the branching unitaccording to the embodiment of the present invention; view (a)illustrates characteristics with respect to a blue laser beam; view (b)illustrates characteristics with respect to a green laser beam; view (c)illustrates characteristics with respect to a red laser beam;

FIG. 6 illustrates arithmetic processing according to the embodiment ofthe present invention; and

FIG. 7 is a chromaticity diagram for illustrating the arithmeticprocessing according to the embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is applicable to various image display apparatuseseach synthesizing laser beams of different color components output froma plurality of laser beam source portions to display a color image, butas an example of applying the present invention, the structure of alaser projector synthesizing laser beams of three color components of ared color component (R), a green color component (G), and a blue colorcomponent (B) and scanning this synthesized beam by a scan mirror toproject and display a color image on a projection surface is nowdescribed. A state of creating a white balance in the synthesized beamis described as an example, but it is clear from the followingdescription that another prescribed color state can be created accordingto the present invention.

FIG. 1 illustrates an example of a laser projector 1, and this laserprojector 1 is mainly constituted by laser beam sources 2 a to 2 c,various optical elements (dichroic mirrors 3 and 4 and a lens 5), a scanmirror 6, and various drive/control units (a scan mirror driver 7, ascan mirror control portion 8, an image processing portion 9, a lasercontrol portion 10, and a laser driver 11). The laser projector 1synthesizes laser beams of color components of red, blue, and green, andthereafter projects the synthesized beam on a projection surface A, suchas a screen or a wall, thereby displaying a color image according to aninput video signal on the projection surface A. The laser projector 1 isan example of the “image display apparatus” in the present invention.

The laser beam sources 2 a to 2 c are laser diodes (LDs) outputtinglaser beams of different color components and are driven independentlyof each other by the driving current individually supplied from thelaser driver 11 to output laser beams of single color components. Thus,the laser beams of the single color components of specified wavelengthsare emitted. In other words, a laser beam of a blue color component (B)is emitted from the laser beam source 2 a, a laser beam of a green colorcomponent (G) is emitted from the laser beam source 2 b, and a laserbeam of a red color component (R) is emitted from the laser beam source2 c. The laser beam source 2 a is an example of the “laser beam sourceportion” or the “blue laser beam source” in the present invention. Thelaser beam source 2 b is an example of the “laser beam source portion”or the “green laser beam source” in the present invention. The laserbeam source 2 c is an example of the “laser beam source portion” or the“red laser beam source” in the present invention.

The dichroic mirrors 3 and 4 transmit only laser beams of specifiedwavelengths and reflect others thereby synthesizing the laser beams ofthe color components of R, G, and B emitted from the laser beam sources2 a to 2 c. Specifically, the laser beams of the blue color componentand the green color component emitted from the laser beam sources 2 aand 2 b are synthesized in the dichroic mirror 3 on the upstream of anoptical path, and thereafter are emitted to the dichroic mirror 4 on thedownstream of the optical path. This emitted synthesized beam and thelaser beam of the red color component emitted from the laser beam source2 c are further synthesized in the dichroic mirror 4, and are emitted asa targeting final color-synthesized beam. The dichroic mirrors 3 and 4include optical portions synthesizing the laser beams of the colorcomponents of R, G, and B, and the color-synthesized beam obtained bythis synthesis is incident on the scan mirror 6 through the lens 5. Thedichroic mirrors 3 and 4 are examples of the “synthesized beamgeneration portion” in the present invention.

According to this embodiment, as the scan mirror 6, a MEMS (microelectro mechanical system) scan mirror advantageous for downsizing, lowpower consumption, speeding up of processing, etc. is employed. The scanmirror 6 is displaced in a horizontal direction (direction X) and avertical direction (direction Y) by the scan mirror driver 7 into whicha driving signal is input from the scan mirror control portion 8,reflects the color beam incident on the scan mirror 6 according to thedeflection angle of the scan mirror 6, and projects the same on theprojection surface A. The scan mirror 6 is an example of the “scanportion” in the present invention.

The image processing portion 9 transmits video data to the laser controlportion 10 at prescribed time intervals on the basis of a video signalinput from an external device such as a personal computer, whereby thelaser control portion 10 obtains pixel information at a prescribed scanposition. The laser control portion 10 controls the laser driver 11 witha driving current waveform signal in order to project an image includinga plurality of pixels on a projection range on the basis of the pixelinformation. Furthermore, the laser control portion 10 controls theoutputs of the laser beam sources 2 a to 2 c according to the lightquantities of the branched laser beams of the color components of R, G,and B detected by a detector 12. The laser control portion 10 is anexample of the “control portion” in the present invention.

According to this embodiment, the laser control portion 10 controls theoutputs of the laser beam sources 2 a to 2 c through the laser driver 11in order to create a white balance on the basis of the detection resultof the detector 12, as described later. Furthermore, according to thisembodiment, the laser control portion 10 drives all the laser beamsources 2 a to 2 c to allow a laser beam source for any one of the threecolor components to output a laser beam during image display with thesynthesized beam of the three color components and executes a mode inwhich the outputs of laser beams from laser beam sources for theremaining color components are stopped every frame or every severalframes of a projection image, as described later. In other words, alaser beam of a single color component of R, G, and B is output for avery short period of time during image display with the synthesizedbeam, and the laser beam of the single color component is output withrespect to each of R, G, and B. Thus, the laser control portion 10 isconfigured to switch between a first mode in which an image iscontinuously displayed without detection of the light quantity and asecond mode in which the laser beam is output from the laser beam source2 a, 2 b, or 2 c for any one of the color components during imagedisplay with the synthesized beam and the light quantity of the laserbeam is detected. As the second mode, an existing mode employed tocorrect the outputs of the laser beam source portions during imagedisplay may be utilized.

The laser driver 11 drives the laser beam sources 2 a to 2 c to allowthe laser beam sources 2 a to 2 c to emit the laser beams on the basisof the aforementioned control performed by the laser control portion 10.The laser beam sources 2 a to 2 c emit the laser beams when currentgreater than or equal to the vibration threshold current is suppliedfrom the laser driver 11 and output the laser beams having largeroutputs (light quantities) as the value of the supplied currentincreases. Furthermore, the laser beam sources 2 a to 2 c stopoutputting the laser beams when current less than the vibrationthreshold current is supplied. According to this embodiment, as thelaser beam sources 2 a to 2 c, the laser diodes (LDs) are employed.

According to this embodiment, a branching unit 13 is provided in theoptical path of the color synthesized beam between the dichroic mirror 4and the lens 5. In other words, the branching unit 13 is arrangedbetween the dichroic mirror 4 and the scan mirror 6 in the optical pathof the synthesized beam. The branching unit 13 branches an incident beaminto a beam guided to the scan mirror 6 and a beam guided to thedetector 12 with a dielectric multi-layer 15 having prescribedreflectance characteristics. This branched beam is applied to thedetector 12, and a signal indicating the light quantity detected by thedetector 12 is input into the laser control portion 10.

The branching unit 13 according to this embodiment is a prism 14 formedwith a reflective film having prescribed reflectance characteristics onone end surface, as shown in FIG. 2, and the incident beam is reflectedby this reflective film with a prescribed reflectance and is incident onthe detector 12. The transmitted beam is incident on the scan mirror 6through the lens 5. According to this embodiment, as this reflectivefilm, the dielectric multi-layer 15 is employed. According to thisembodiment, the beam reflected by the branching unit 13 is incident onthe detector 12, but the branching unit 13 may be allowed to haveprescribed transmittance characteristics, the beam transmitted throughthe branching unit 13 may be incident on the detector 12, and thereflected beam may be incident on the scan mirror 6.

According to this embodiment, the branching unit is configured to have areflectance with increase/decrease characteristics opposite to theincrease/decrease characteristics of the outputs of the laser beams inincreasing or decreasing the outputs of the laser beams of the colorcomponents of R, G, and B according to changes of the wavelengths of thelaser beams of the color components of R, G, and B in order to maintainthe white balance of the synthesized beam.

Specifically, the branching unit 13 is so configured that thereflectance thereof is changed in response to a change of the wavelengthof the laser beam. As shown in FIG. 3, the branching unit 13 is soconfigured that the reflectance thereof is decreased when the wavelengthof the laser beam in the range of blue and the wavelength of the laserbeam in the range of red are increased and the reflectance thereof isincreased when the wavelength of the laser beam in the range of green isincreased. Furthermore, the branching unit 13 is so configured that thereflectance (about 10%) for the laser beam of the blue color componentis highest, the reflectance (about 2%) for the laser beam of the redcolor component is lowest, and the reflectance (about 4%) for the laserbeam of the green color component is between the reflectance for thelaser beam of the blue color component and the reflectance for the laserbeam of the red color component.

According to this embodiment, a mode in which the laser control portion10 allows the laser beam sources 2 a to 2 c to output the laser beams ofthe single color components of R, G, and B, as described above, atintervals of one or several frames during projection display of a colorimage with the synthesized beam of R, G, and B is employed, and thebranching unit 13 provided in the optical path of the synthesized beamdetects the light quantities of the laser beams of the single colorcomponents of R, G, and B at the timing when these laser beams of thesingle color components are output. Therefore, the laser control portion10 controls increase and decrease of the outputs of the laser beamsources 2 a to 2 c in order to create the white balance on the basis ofthe light quantities of R, G, and B detected by the detector 12according to the aforementioned timing.

Specifically, the laser control portion 10 is configured to decrease theoutput of a laser beam source for a color component whose detected lightquantity is increased of the laser beam sources 2 a to 2 c and increasethe output of a laser beam source for a color component whose detectedlight quantity is decreased of the laser beam sources 2 a to 2 caccording to the light quantities of the branched laser beams of thecolor components of R, G, and B detected by the detector 12.

For example, the laser control portion 10 is configured to increase theoutputs of the laser beam source 2 a outputting the laser beam of theblue color component and the laser beam source 2 c outputting the laserbeam of the red color component and decrease the output of the laserbeam source 2 b outputting the laser beam of the green color componentwhen the wavelengths of the laser beams of the color components of R, G,and B output from the laser beam sources are increased due to increasein temperature.

The laser control portion 10 is configured to allow the laser beamsource 2 a, 2 b, or 2 c for any one of the color components of R, G, andB to output the laser beam during image display with the synthesizedbeam. Specifically, the laser control portion 10 is configured to allowthe laser beam sources 2 a to 2 c one by one to sequentially output thelaser beams at intervals of a prescribed number of frames (at theintervals of one or several frames, for example) during image displaywith the synthesized beam and control the outputs of the laser beamsources 2 a to 2 c according to the light quantities of the branchedlaser beams of the color components of R, G, and B detected by thedetector 12.

According to this embodiment, the branching unit 13 is provided in theoptical path of the synthesized beam, so that the branching unit 13 isshared for the color components of R, G, and B, but the branching unit13 and the detector 12 may be provided in the optical path of each ofthe laser beams of the single color components of R, G, and B. In thiscase, the aforementioned mode is not required.

When the wavelengths of the laser beams of the single color componentsof the R, G, and B output from the laser beam sources 2 a to 2 c changedue to a temperature change in a state where the laser beams of thesingle color components of R, G, and B have a prescribed output ratio tocreate the white balance, the white balance is lost unless theprescribed output ratio is achieved with these changed wavelengths. Thereflectance characteristics of the dielectric multi-layer 15 areutilized to control the outputs of the laser beam sources in order tomaintain the white balance in this manner.

As the wavelength of the laser beam of the blue color component (B)changes in the range of about 450 nm due to a temperature change, forexample, the wavelengths of the laser beams of the color components ofR, G, and B change in certain ranges in response to a possibletemperature change. The dielectric multi-layer 15 has suchcharacteristics that the reflectance changes in the wavelength changeranges of the laser beams of the color components of R, G, and B due toa temperature change in an example shown in FIG. 3, and thesereflectance characteristics are opposite to such characteristics thatthe outputs of the laser beams of the color components of R, G, and Bare increased or decreased with respect to changes of the wavelengths ofthe laser beams of the color components of R, G, and B, as describedabove.

The example shown in FIG. 3 exhibits such reflectance characteristicsthat as to the laser beam of the blue color component (B), thereflectance is decreased after the wavelength passes through about 450nm, as to the laser beam of the green color component (G), thereflectance is increased after the wavelength passes through about 510nm, and as to the laser beam of the red color component (R), thereflectance is decreased when the wavelength is increased. The detailsaccording to this embodiment are shown in FIG. 5.

Output control of the laser beam sources 2 a to 2 c utilizing thereflectance characteristics of the dielectric multi-layer 15 is nowdescribed. FIG. 4 illustrates examples of the wavelengths and outputs ofthe laser beams of R, G, and B according to the temperature. View (a) ofFIG. 4 illustrates characteristics in which the white balance (whitedisplay) is created at the temperature of 25° C., view (b) of FIG. 4illustrates characteristics in which the temperature changes to 50° C.and the white balance is lost, and view (c) of FIG. 4 illustratescharacteristics for maintaining the white balance and brightness at thetemperature of 50° C.

As shown in view (a) of FIG. 4, at the temperature of 25° C., the laserbeam of the red color component (R) output from the laser beam source 2c has a wavelength of 638 nm and an output of P mW, the laser beam ofthe green color component (G) output from the laser beam source 2 b hasa wavelength of 515 nm and an output of 0.76 P mW, and the laser beam ofthe blue color component (B) output from the laser beam source 2 a has awavelength of 450 nm and an output of 0.55 P mW. By these relationshipsbetween the wavelengths and the outputs, the white balance is created at12.0 lm. The outputs of the laser beams from the laser beam sources arerepresented based on the output P mW of the red color component (R) atthe temperature of 25° C.

When the temperature changes from this state to 50° C., the laser beamof the red color component (R) output from the laser beam source 2 c hasa wavelength of 643 nm and an output of P mW, the laser beam of thegreen color component (G) output from the laser beam source 2 b has awavelength of 517 nm and an output of 0.76 P mW, and the laser beam ofthe blue color component (B) output from the laser beam source 2 a has awavelength of 452 nm and an output of 0.55 P mW, as shown in view (b) ofFIG. 4. The wavelengths and outputs vary, and the white balance is lostat 11.9 lm.

In order to maintain the white balance and brightness at the temperatureof 50° C., the laser beam of the red color component (R) output from thelaser beam source 2 c must have a wavelength of 643 nm and an output of1.21 P mW, the laser beam of the green color component (G) output fromthe laser beam source 2 b must have a wavelength of 517 nm and an outputof 0.72 P mW, and the laser beam of the blue color component (B) outputfrom the laser beam source 2 a must have a wavelength of 452 nm and anoutput of 0.56 P mW, as shown in view (c) of FIG. 4. In other words,unless the outputs of the laser beam sources 2 a to 2 c are controlledaccording to a temperature change, the proper outputs of the laser beamsources according to a wavelength change cannot be obtained, and hencethe white balance cannot be maintained, as shown in view (b) of FIG. 4.

These relationships between the wavelengths of the laser beams of thecolor components of R, G, and B and the outputs of the laser beams ofthe color components for creating the white balance can be obtained byan experiment. These relationships can be also obtained from thefollowing publicly known calculation.

An example of calculating an RGB ratio (an output ratio) for creatingthe white balance, setting the wavelengths of R, G, and B to 637 nm, 510nm, and 445 nm, respectively and representing the ratio as a:b:c is nowdescribed. As shown in FIG. 6, tristimulus values (X, Y, Z) are firstobtained from a color-matching function (according to this embodiment,CIE1931 (Commission Internationale de l'Eclairage, 1931)) and thespectral sensitivities of the laser beam sources (RGB ratio). Accordingto this embodiment, the tristimulus values are obtained asX=0.34225*a+0.0093*b+0.506160*c, Y=0.03050*a+0.5030*b+0.20200*c, andZ=1.75950*a+0.1582*b+0.000029*c. Then, the ratio of these tristimulusvalues (X, Y, Z) is quantified as chromaticity x and y. According tothis embodiment, the ratio of these tristimulus values (X, Y, Z) isquantified as x=X/(X+Y+Z) and y=Y/(X+Y+Z). Then, the RGB ratio is soadjusted that this chromaticity (x, y) becomes white (x=0.33 and y=0.33,for example) in a chromaticity diagram shown in FIG. 7 (in FIG. 7, Rrepresents a red region, G represents a green region, and B represents ablue region). According to this embodiment, the white balance is createdwhen the RGB ratio is 3.4:2.7:1.0.

In order to maintain the white balance even when the temperature changesfrom 25° C. to 50° C. as described above, the laser control portion 10performs control of increasing the output of the laser beam of the redcolor component (R) from P mW to 1.21 P mW, decreasing the output of thelaser beam of the green color component (G) from 0.76 P mW to 0.72 P mW,and increasing the output of the laser beam of the blue color component(B) from 0.55 P mW to 0.56 P mW on the laser beam sources 2 a to 2 c.

This output control of the laser beam sources 2 a to 2 c performed bythe laser control portion 10 is performed according to the lightquantities of the color components of R, G, and B detected by thedetector 12, and the laser control portion 10 performs control ofdecreasing the outputs of the laser beam sources when the detected lightquantities are large and increasing the outputs of the laser beamsources when the detected light quantities are small. The branching unit13 (the dielectric multi-layer 15) has reflectance characteristicsopposite to the characteristic of increasing or decreasing the outputsby the laser control portion 10 in control of increasing or decreasingthe outputs correspondingly to a wavelength change in order to createthe white balance, and hence the branching unit 13 reflects beams of thecorresponding light quantities and allows the beams to be incident onthe detector 12 in order to control the outputs such that the whitebalance is created with the changed wavelengths.

In the examples shown in FIG. 4, when the temperature changes from 25°C. to 50° C., the wavelength of the laser beam of the blue colorcomponent (B) changes from 450 nm to 452 nm, the wavelength of the laserbeam of the green color component (G) changes from 515 nm to 517 nm, andthe wavelength of the laser beam of the red color component (R) changesfrom 638 nm to 643 nm. With respect to these changes of the wavelengths,the dielectric multi-layer 15 exhibits the reflectance characteristicsshown in FIG. 5, and hence the aforementioned output control based onthe detected light quantities of the reflected beams is properlyperformed by the laser control portion 10 while the white balance ismaintained.

In other words, as shown in view (a) of FIG. 5, with respect to thelaser beam of the blue color component (B) whose wavelength changes from450 nm to 452 nm, the reflectance of the dielectric multi-layer 15 isdecreased from 10% to 9.7%. Thus, the light quantity of this reflectedbeam detected by the detector 12 is decreased, so that the laser controlportion 10 performs control of increasing the output of the laser beamsource 2 a for the blue color component (B) from 0.55 P mW to 0.56 P mW.

Furthermore, as shown in view (b) of FIG. 5, with respect to the laserbeam of the green color component (G) whose wavelength changes from 515nm to 517 nm, the reflectance of the dielectric multi-layer 15 isincreased from 4% to 4.2%. Thus, the light quantity of this reflectedbeam detected by the detector 12 is increased, so that the laser controlportion 10 performs control of decreasing the output of the laser beamsource 2 b for the green color component (G) from 0.76 P mW to 0.72 PmW.

In addition, as shown in view (a) of FIG. 5, with respect to the laserbeam of the red color component (R) whose wavelength changes from 638 nmto 643 nm, the reflectance of the dielectric multi-layer 15 is decreasedfrom 2% to 1.7%. Thus, the light quantity of this reflected beamdetected by the detector 12 is decreased, so that the laser controlportion 10 performs control of increasing the output of the laser beamsource 2 c for the red color component (R) from P mW to 1.21 P mW.Therefore, the white balance of the synthesized beam of R, G, and B ismaintained even at the temperature of 50° C.

According to this embodiment, as hereinabove described, the laserprojector 1 is provided with the branching unit 13 having thereflectance with the increase/decrease characteristics opposite to theincrease/decrease characteristics of the outputs of the laser beams inincreasing or decreasing the outputs of the laser beams of the colorcomponents of R, G, and B according to changes of the wavelengths of thelaser beams of the color components of R, G, and B in order to maintainthe white balance of the synthesized beam, whereby even when thewavelengths of the laser beams change, the outputs of the laser beamsources 2 a to 2 c are controlled according to the light quantities ofthe laser beams of the color components of R, G, and B branched by thebranching unit 13 and detected by the detector 12, so that the whitebalance can be maintained.

According to this embodiment, as hereinabove described, the lasercontrol portion 10 is configured to decrease the outputs of the laserbeam sources 2 a to 2 c for the color components whose detected lightquantities are increased and increase the outputs of the laser beamsources 2 a to 2 c for the color components whose detected lightquantities are decreased according to the light quantities of thebranched laser beams of the color components of R, G, and B detected bythe detector 12. Thus, the outputs of the laser beam sources 2 a to 2 care adjusted in such directions as to cancel the changes of the detectedlight quantities, whereby the white balance can be easily maintained.

According to this embodiment, as hereinabove described, the lasercontrol portion 10 is configured to increase the outputs of the laserbeam source 2 a outputting the laser beam of the blue color componentand the laser beam source 2 c outputting the laser beam of the red colorcomponent and decrease the output of the laser beam source 2 boutputting the laser beam of the green color component when thewavelengths of the laser beams of the color components of R, G, and Boutput from the laser beam sources are increased due to a temperaturerise. Thus, even when the wavelengths of the laser beams of the colorcomponents of R, G, and B output from the laser beam sources 2 a to 2 care increased due to a temperature rise, the white balance can be easilymaintained by increasing the outputs of the laser beam source 2 a andthe laser beam source 2 c and decreasing the output of the laser beamsource 2 b.

According to this embodiment, as hereinabove described, the branchingunit 13 is so configured that the reflectance thereof changes accordingto the changes of the wavelengths of the laser beams. Thus, the changesof the wavelengths of the laser beams can be easily detected by thechanges of the light quantities of the laser beams of the colorcomponents of R, G, and B branched by the branching unit 13.

According to this embodiment, as hereinabove described, the branchingunit 13 is so configured that the reflectance thereof decreases when thewavelengths of the laser beam of the blue color component and the laserbeam of the red color component are increased and increases when thewavelength of the laser beam of the green color component is increased.Thus, the changes of the wavelengths of the laser beams of the blue,red, and green color components are easily detected and the outputs ofthe laser beam sources for the blue, red, and green color components areadjusted by the control portion, whereby the white balance can be easilymaintained.

According to this embodiment, as hereinabove described, the branchingunit 13 is so configured that the reflectance thereof for the laser beamof the blue color component is highest, the reflectance thereof for thelaser beam of the red color component is lowest, and the reflectancethereof for the laser beam of the green color component is between thereflectance for the laser beam of the blue color component and thereflectance for the laser beam of the red color component. Thus, thelight quantity of the laser beam of the blue color component whosewavelength is short and for which the detection sensitivity is low,being incident on the detector 12 is increased, and the light quantityof the laser beam of the red color component whose wavelength is longand for which the detection sensitivity is high, being incident on thedetector 12 is decreased. Therefore, the detector 12 can reliably detectthe laser beams of the red color component, the green color component,and the blue color component without increasing the range of thedetection sensitivity of the detector 12 for the laser beams.

According to this embodiment, as hereinabove described, the branchingunit 13 is configured to include the prism 14 formed with the dielectricmulti-layer 15 having the reflectance with the increase/decreasecharacteristics opposite to the increase/decrease characteristics of theoutputs of the laser beams. Thus, due to the dielectric multi-layer 15,the branching unit 13 having the reflectance with the increase/decreasecharacteristics opposite to the increase/decrease characteristics of theoutputs of the laser beams in increasing or decreasing the outputs ofthe laser beams of the color components of R, G, and B according to thechanges of the wavelengths of the laser beams of the color components ofR, G, and B in order to maintain the prescribed color state of thesynthesized beam can be easily provided. Furthermore, the branching unit13 includes the prism 14 formed with the dielectric multi-layer 15,whereby the branching unit can be employed with the function of theprism 14 in addition to a function of branching the beam.

According to this embodiment, as hereinabove described, the branchingunit 13 is provided in the optical path of the synthesized beam, and thelaser control portion 10 is configured to allow the laser beam source 2a, 2 b, or 2 c for any one of the color components to output the laserbeam during image display with the synthesized beam and control theoutput of the corresponding laser beam source 2 a, 2 b, or 2 c accordingto the light quantity of the branched laser beam of the single colorcomponent detected by the detector 12. Thus, the branching unit 13 andthe detector 12 can be shared for the color components of R, G, and B,and hence the number of components can be reduced.

According to this embodiment, as hereinabove described, the lasercontrol portion 10 is configured to allow a plurality of laser beamsources 2 a to 2 c one by one to sequentially output the laser beamsduring image display with the synthesized beam and control the outputsof the laser beam sources 2 a to 2 c according to the light quantitiesof the branched laser beams of the color components of R, G, and Bdetected by the detector 12. Thus, the laser beams of the colorcomponents of R, G, and B can be detected individually, and hence thechanges of the light quantities of the laser beams of the colorcomponents of R, G, and B can be more accurately detected.

According to this embodiment, as hereinabove described, the lasercontrol portion 10 is configured to allow the laser beam source 2 a, 2b, or 2 c for any one of the color components to output the laser beamfor detecting the light quantity at the intervals of the prescribednumber of frames during image display with the synthesized beam andcontrol the output of the corresponding laser beam source 2 a, 2 b, or 2c according to the light quantity of the branched laser beam of thesingle color component detected by the detector 12. Thus, even when thewavelength of the laser beam changes during image display, the output ofthe corresponding laser beam source 2 a, 2 b, or 2 c can be adjustedaccording to the change of the light quantity detected by the detector12, and hence the white balance state during image display can be easilymaintained.

According to this embodiment, as hereinabove described, the lasercontrol portion 10 is configured to switch between the first mode inwhich an image is continuously displayed without detection of the lightquantity and the second mode in which the laser beam is output from thelaser beam source 2 a, 2 b, or 2 c for any one of the color componentsduring image display with the synthesized beam and the light quantity ofthe laser beam is detected. Thus, the white balance state during imagedisplay can be easily maintained by the second mode while the image iscontinuously smoothly displayed without detection of the light quantityby the first mode.

According to this embodiment, as hereinabove described, the branchingunit 13 is arranged between the dichroic mirror 4 and the scan mirror 6in the optical path of the synthesized beam. Thus, the branching unit 13can be arranged at a position on which the laser beams of the colorcomponents of R, G, and B are focused, and hence increase in the size ofthe branching unit 13 can be inhibited.

The embodiment disclosed this time must be considered as illustrative inall points and not restrictive. The range of the present invention isshown not by the above description of the embodiment but by the scope ofclaims for patent, and all modifications within the meaning and rangeequivalent to the scope of claims for patent are further included.

For example, while the present invention is applied to the laserprojector in the aforementioned embodiment, the present invention is notrestricted to this. The present invention may alternatively be appliedto an image display apparatus other than the laser projector.

While the present invention is applied to the state where the whitebalance is created as the prescribed color state in the aforementionedembodiment, the present invention is not restricted to this. Forexample, the prescribed color state may alternatively be settableaccording to design, user's preference, or the like.

While the branching unit includes the prism formed with the dielectricmulti-layer in the aforementioned embodiment, the present invention isnot restricted to this. According to the present invention, a branchingunit other than the dielectric multi-layer may alternatively beemployed.

While the branching unit is provided in the optical path of thesynthesized beam in the aforementioned embodiment, the present inventionis not restricted to this. According to the present invention, abranching unit may alternatively be provided for each of the laser beamsource portions for the color components and detect the light quantityof the laser beam of each color component, for example.

While the laser beam source portions include the laser beam source forthe red color component, the laser beam source for the green colorcomponent, and the laser beam source for the blue color component in theaforementioned embodiment, the present invention is not restricted tothis. According to the present invention, the laser beam source portionmay alternatively be configured to include laser beam sources foranother color combination so far as a plurality of different colorcomponents are included.

What is claimed is:
 1. An image display apparatus comprising: aplurality of laser beam source portions outputting laser beams of aplurality of color components different from each other; a synthesizedbeam generation portion synthesizing the laser beams of the plurality ofcolor components to generate a synthesized beam; a control portioncontrolling outputs of the laser beam source portions; a branching unitbranching the laser beams of the color components; and a detectionportion detecting light quantities of the laser beams of the colorcomponents branched by the branching unit, wherein the branching unithas a reflectance or transmittance with increase/decreasecharacteristics opposite to increase/decrease characteristics of outputsof the laser beams in increasing or decreasing the outputs of the laserbeams of the color components according to changes of wavelengths of thelaser beams of the color components in order to maintain a prescribedcolor state of the synthesized beam, and the control portion isconfigured to control the outputs of the laser beam source portionsaccording to light quantities of branched laser beams of the colorcomponents detected by the detection portion.
 2. The image displayapparatus according to claim 1, wherein the control portion isconfigured to decrease the outputs of the laser beam source portions forthe color components whose detected light quantities are increased andincrease the outputs of the laser beam source portions for the colorcomponents whose detected light quantities are decreased according tothe light quantities of the branched laser beams of the color componentsdetected by the detection portion.
 3. The image display apparatusaccording to claim 1, wherein the control portion is configured toincrease outputs of a blue laser beam source outputting a laser beam ofa blue color component and a red laser beam source outputting a laserbeam of a red color component and decrease an output of a green laserbeam source outputting a laser beam of a green color component when thewavelengths of the laser beams of the color components output from thelaser beam source portions are increased due to a temperature rise. 4.The image display apparatus according to claim 1, wherein the branchingunit is so configured that the reflectance or transmittance thereofchanges according to the changes of the wavelengths of the laser beams.5. The image display apparatus according to claim 4, wherein thebranching unit is so configured that the reflectance or transmittancethereof decreases when wavelengths of a laser beam of a blue colorcomponent and a laser beam of a red color component are increased andincreases when a wavelength of a laser beam of a green color componentis increased.
 6. The image display apparatus according to claim 1,wherein the branching unit is so configured that the reflectance ortransmittance thereof for a laser beam of a blue color component ishighest, the reflectance or transmittance thereof for a laser beam of ared color component is lowest, and the reflectance or transmittancethereof for a laser beam of a green color component is between thereflectance or transmittance thereof for the laser beam of the bluecolor component and the reflectance or transmittance thereof for thelaser beam of the red color component.
 7. The image display apparatusaccording to claim 1, wherein the prescribed color state comprises astate where a white balance of the synthesized beam is created.
 8. Theimage display apparatus according to claim 1, wherein the branching unitincludes a prism formed with a dielectric multi-layer having areflectance or transmittance with increase/decrease characteristicsopposite to the increase/decrease characteristics of the outputs of thelaser beams.
 9. The image display apparatus according to claim 1,wherein the branching unit is provided in an optical path of thesynthesized beam, and the control portion is configured to allow a laserbeam source portion for any one of the color components to output alaser beam during image display with the synthesized beam and control anoutput of the laser beam source portion according to a light quantity ofa branched laser beam of a single color component detected by thedetection portion.
 10. The image display apparatus according to claim 9,wherein the control portion is configured to allow the plurality oflaser beam source portions one by one to sequentially output the laserbeams during the image display with the synthesized beam and control theoutputs of the laser beam source portions according to the lightquantities of the branched laser beams of the color components detectedby the detection portion.
 11. The image display apparatus according toclaim 9, wherein the control portion is configured to allow the laserbeam source portion for any one of the color components to output thelaser beam for detecting the light quantity at an interval of aprescribed number of frames during the image display with thesynthesized beam and control the output of the laser beam source portionaccording to the light quantity of the branched laser beam of the singlecolor component detected by the detection portion.
 12. The image displayapparatus according to claim 9, wherein the control portion isconfigured to switch between a first mode in which an image iscontinuously displayed without detection of the light quantity and asecond mode in which the laser beam is output from the laser beam sourceportion for any one of the color components during the image displaywith the synthesized beam and the light quantity of the laser beam isdetected.
 13. The image display apparatus according to claim 1, furthercomprising a scan portion scanning the synthesized beam, wherein thebranching unit is arranged between the synthesized beam generationportion and the scan portion in an optical path of the synthesized beam.14. The image display apparatus according to claim 13, wherein the scanportion comprises a MEMS scan mirror.
 15. The image display apparatusaccording to claim 1, wherein the synthesized beam generation portionincludes a dichroic mirror.
 16. An optical component having areflectance or transmittance with increase/decrease characteristicsopposite to increase/decrease characteristics of outputs of laser beamsin increasing or decreasing the outputs of the laser beams of aplurality of color components according to changes of wavelengths of thelaser beams of the color components in order to maintain a synthesizedbeam obtained by synthesizing the laser beams of the color components ina prescribed color state, the optical component provided in an imagedisplay apparatus comprising a detection portion detecting lightquantities of the laser beams and a control portion controlling outputsof a plurality of laser beam source portions outputting the laser beamsof the plurality of color components different from each other accordingto detection results of the detection portion, including a branchingunit branching the laser beams of the color components and guiding thelaser beams to the detection portion.
 17. The optical componentaccording to claim 16, wherein the control portion is configured todecrease the outputs of the laser beam source portions for the colorcomponents whose detected light quantities are increased and increasethe outputs of the laser beam source portions for the color componentswhose detected light quantities are decreased according to lightquantities of branched laser beams of the color components detected bythe detection portion.
 18. The optical component according to claim 16,wherein the branching unit is so configured that a reflectance ortransmittance thereof changes according to the changes of thewavelengths of the laser beams.
 19. The optical component according toclaim 18, wherein the branching unit is so configured that thereflectance or transmittance thereof decreases when wavelengths of alaser beam of a blue color component and a laser beam of a red colorcomponent are increased and increases when a wavelength of a laser beamof a green color component is increased.
 20. The optical componentaccording to claim 16, wherein the branching unit is so configured thatthe reflectance or transmittance thereof for a laser beam of a bluecolor component is highest, the reflectance or transmittance thereof fora laser beam of a red color component is lowest, and the reflectance ortransmittance thereof for a laser beam of a green color component isbetween the reflectance or transmittance thereof for the laser beam ofthe blue color component and the reflectance or transmittance thereoffor the laser beam of the red color component.